When Education Edition is enabled, adding the minecraft:balloonable component to the player.json entity file then attaching a balloon to a player in-game affects the server-sided player, but not the client-sided player.

Expected: When attached to a balloon, a player will rise (or fall) depending on the given mass in the minecraft:balloonable component. The player will also be slightly moved by the movement of the balloon.

Result: When attached to a balloon, the CLIENT-SIDED player will behave expectedly, but the SERVER-SIDED player will NOT behave expectedly.